We propose to utilize a technique to estimate the secretory capacity of pancreatic beta cells in diabetic patients to determine whether the hyperglycemia is predominantly due to primary failure of the beta cells to release isulin. Similarly we will assess insulin sensitivity of these diabetics to characterize those whose hyperglycemia is primarily due to insulin resistance. After classifying diabetes into these two major types, we will correlate early vascular abnormalities in each of these types to see if there is any greater prevalence: 1) leakage of retinal capillaries (photofluorometry), or 2) myocardiopathy (echocardiography) in one of the types of diabetes. We feel that a improved classification of idiopathic diabetes mellitus will be advantageous not only in better ascertaining the incidence of vascular disease and its relation to the types of diabetes, but also in clarifying questions relating to the etiology pathogenesis and heredity of Diabetes Mellitus.